Increased antioxidant activity in bronchoalveolar lavage fluid after acute lung injury in anesthetized sheep

OBJECTIVE: To determine if bronchoalveolar lavage fluid is a more potent antioxidant after acute lung injury in a sheep model compared with the baseline condition. DESIGN: Nonrandomized, controlled study, with repeated measures. SETTING: University research laboratory. SUBJECTS: Seven healthy adult sheep (25 to 50 kg) were studied with five experimental sheep and two control sheep. INTERVENTIONS: Sheep with lung-lymph fistulas were used to study the antioxidant activity of serum, lymph, and bronchoalveolar lavage fluid, both at baseline and after the iv infusion of endotoxin and subsequent induction of acute lung injury. Antioxidant activity was measured, and it reflects the ability of serum, lymph, and bronchoalveolar lavage fluid to inhibit lipid peroxidation. MEASUREMENTS AND MAIN RESULTS: When compared at several volumes, bronchoalveolar lavage fluid after acute lung injury was a more potent inhibitor of lipid peroxidation than bronchoalveolar lavage fluid at baseline. In contrast, antioxidant activity in both serum (69.6 +/- 4.5% vs. 47.2 +/- 4.6%; p = .001) and lymph (45.0 +/- 2.3% vs. 31.9 +/- 1.2%; p = .001) decreased with acute lung injury. CONCLUSIONS: These findings suggest that the alveolar fluid after acute lung injury possesses enhanced antioxidant activity that is likely due to the influx of serum proteins. Thus, the high permeability pulmonary edema of acute lung injury, while detrimental to gas exchange, may be beneficial in preventing further oxidant-mediated lung injury.